Viruses carried to soil by irrigation can be aerosolized later during windy spells

International audienceReclaiming domestic wastewaters for irrigation helps to meet increasing water needs, to reduce discharge to conventional waters, and to fertilize soils. Unfortunately, it also contaminates crop and soil with human enteric pathogens. However, partial aerosolization of pathogens deposited on soil surface during windy periods has never been studied. Here, we investigated this putative aerosolization of pathogens from soil surface during windy periods by using murine mengoviruses, a surrogate of human enteric viruses, and assess the impact of environmental conditions on this phenomenon. Wind tunnel experiments were carried out on viruscontaminated plots submitted to various wind, soil surface moisture, and water types. Aerosolized viruses were trapped by impingers for RT-qPCR quantification. Virus concentrations were corrected for partial virus trapping efficiency and reaerosolization. A mathematical model was devised for one or more virus groups, characterized by their number of viruses and their kinetic aerosolization coefficient. The model was fitted to real trial data and used to generate numerical experiments to study the model estimators. We showed that 1 to 15 % of viruses carried to soil were aerosolized, of which 11 to 89%during the first 0.5 h. The viruses fell into two groups: a group that get aerosolized near instantaneously and a group that get aerosolized gradually. The range of kinetic coefficients of aerosolization of the gradually aerosolized group accounted for 90 % of viruses of this group aerosolized after 0.5–10.6 days. The size of this group increased with wind speed, decreased with soil warming, and increased with organic content of spray water. This first study on virus aerosolization shows that aerosolization cannot be neglected both in terms of quantities and speeds. Combined with virus stability in air, we anticipate our model to help policymakers refine regulations and standards governing wastewater reuse in irrigation